Short Message Service (SMS) is commonly used in Global System of Mobile (GSM), Global Position System (GPS), assisted-GPS (AGPS), General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA) and other wireless communication systems. Because of its convenience and low price, SMS has become one of important information exchange techniques for mobile devices nowadays and likely continue to be further utilized in the near future in various communication fields.
In the GPRS and CDMA systems, data can be exchanged not only between a mobile phone and a base station, but also between two mobile phones. The mobile phones usually take advantage of SMS as an effective way to transmit short text data between the users. However, in the prior art SMS specifications, only text messages can be exchanged and the size of text messages is very limited. For example, one SMS message can only have 140 bytes of data.
In the GSM system, the SMS specification (GSM SMS specification 03.42 Version 7.1.1) describes a SMS compression standard for transmitting compressed text messages, so the SMS capabilities can be extended. However, this SMS compression standard is seldom used so far because of the low compression rate, and higher cost to design application circuits for data exchange. This SMS compression standard also produces many compatibility problems with some wireless communication systems during the data exchange process.
In addition, some cell phone manufacturers have created some proprietary functions for transmitting ring tones or pictures between cell phones and almost all of the cell phone manufacturers have their own ways to extend the SMS capacity. For example, Nokia, Motorola and Sony have different SMS transmission formats. However, these extensions often are not compatible with each other. Generally, Nokia device users can send special ring tones or pictures between them without any impediment. However, a Nokia device user cannot successfully send a self-programmed ring tone or picture to a Sony device user or Motorola device user. Moreover, some cell phone producers often impose certain strict format and size limitation for messages, such as rings and pictures. For example, only special ring tones in the MIDI format and blank-white point-pictures can be sent between Nokia cell phones.
The disadvantages of low compression rates, proprietary formats and size limitations greatly restrict the SMS applications. It is thus desirous to have a method that extends SMS capabilities so that different sizes of data can be transmitted as short messages between cell phones from different makers thus enabling exchange of different types of data, and it is to such a method the present invention is primarily directed.